| With the acceleration of industrialization,a large amount of industrial wastewater containing toxic heavy metal elements enter the environment,and the accumulation of these heavy metals in the water to a certain extent will cause serious harm to the water,and affect the human health through the way of residential water,eating aquatic animals and so on.Therefore,the effective treatment with heavy metal polluted water is an urgent problem to be solved.Serpentine is a kind of water-bearing magnesium-rich silicate mineral with abundant reserves.It has achieved some results in treating water pollution as an adsorbent.In this paper,the characteristics of cadmium adsorption by serpentine and the optimum conditions of cadmium adsorption by serpentine are optimized by selecting the modified serpentine at the optimum temperature after the characterization of serpentine at different temperatures,and the following main conclusions are obtained:?1?When the modification temperature is 700?,the position and intensity of the X ray diffraction peaks of serpentine have changed greatly compared with that of natural serpentine,and the surface of serpentine cannot see the lamellar structure at all.This indicates that at this time,the crystal structure of serpentine has appeared some changes,the content of O elements of serpentine has decreased,the content of Mg and Si has increased,the change of dihydroxylation has occurred,and the specific surface area and pore volume of serpentine have increased to a large extent.These changes indicate that the adsorption performance of serpentine is enhanced after thermal modification and S-700 shows the best characteristics,and its indexes are relatively high,so the optimum modification temperature is determined to be 700?.?2?Langmuir adsorption isothermal model and quasi-second-order adsorption kinetic model can better describe the adsorption process of cadmium ions by serpentine,which indicates that the adsorption of cadmium ions by serpentine is both monolayer and chemisorption.According to the fitting of the adsorption thermodynamic model for cadmium ions in serpentine adsorbed water,it is concluded that the adsorption process is spontaneous chemical adsorption and endothermic adsorption.?3?Based on the experimental results of the adsorption capacity and adsorption rate of cadmium ions in water adsorbed by serpentine under different influencing factors,it is determined that the approximate values of the four influencing factors are 2% serpentine,6 initial p H of solution,50 mg·L-1 initial concentration of solution and 24 h adsorption time.?4?By optimizing the optimum adsorption conditions of cadmium ions in water adsorbed by serpentine,it is concluded that when the amount of serpentine is 1%,the initial p H of the solution is 5.5,the initial concentration of the solution is 40.83 mg·L-1,the adsorption time is 26.78 h,the adsorption capacity of serpentine to cadmium ions in water is 3.99 mg·g-1,the adsorption rate is 95.24%.After the above best conditions have been verified and the results are similar to the software prediction data,which shows that it is feasible to optimize the conditions for the adsorption of cadmium ions by serpentine by response surface method. |
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